Liquid toner concentrate dispenser for an electrophotographic developing system

ABSTRACT

A valveless pump device is mounted on a threaded cap member and inserted into a toner concentrate flask which is then sealed by screwing down the cap. A reciprocating piston and housing type chamber extends from the cap and is immersed in toner concentrate. A hollow activating rod or tube extends into the flask through the cap and is affixed to the reciprocating piston. Up and down motion of the activating rod varies the capacity of the chamber and effects a two stroke pumping action involving a series of intake apertures and discharge ports located in the variable capacity chamber. During the first stroke the volume of the chamber decreases due to piston movement upward, and the liquid concentrate flows into the hollow center of the activating rod and upwards out of the flask into the electrophotographic developing apparatus. During the second stroke, the piston moves downward and the chamber expands to its original volume. Toner concentrate flows into the chamber through intake ports positioned in the side walls of the piston.

1451 July 31,1973

United States Patent 1191 Levy LIQUID TONER CONCENTRATE Primary Examiner-Robert B. Reeves DISPENSER FOR AN Assistant Examiner Francis I. Bartuska ELECTROPHQTOGRAPHIC DEVELOPING Affoiney-stafiley Z. Cole and Paul Hentzel SYSTEM 7 [7 51 Inventor: Raymond Leon Levy, Palo Alto,

' Calif.

[73] Assignee: Varian Associates, Palo Alto, Calif.

[57] ABSTRACT A valveless pump device is mounted on a threaded cap member and inserted into a toner concentrate flask which is then sealed by screwing down the cap. A reciprocating piston and housing type chamber extends from the cap and is immersed in toner concentrate. A hollow sk through the l 7 9 a l, 9 9 u5 J]. o N .ml mm FA 1] 21 22 ii activating rod or tube extends into the fla cap and is affixed to the reciprocating piston. Up and down motion of the activating rod varies the capacity [52] US. 222/321, 222/385, ZZZ/DIG. l, 4l7/430, 417/557 of the chamber and effects a two stroke pumping action involving a series of intake apertures and discharge ports located in the variable capacity chamber. During the first stroke the volume of the .chamber decreases [51] Int. G01! 11/02 due to piston movement upward, and the liquid concentrate flows into the hollow center of the activating rod and upwards out of the flask i graphic developing apparatus.

[5 6] References Cited nto the electrophotox m B 2 2 2 m m E Tm During the second d the chamber 9/1932 Wickwire, Jr...... 12/1895 stroke, the piston moves downward an exp 551,893 Hardy 950,411 2/1910 ands to its original volume. Toner concentrate flows into the chamber through intake ports positioned in the side walls of the piston.

7 Claims, 2 Drawing Figures LiHi PATENIED m3 1 ma IN ENTOIL YMOND L. EVY

LIQUID TONER CONCENTRATE DISPENSER FOR AN ELECTROPHOTOGRAPHIC DEVELOPING SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a valveless pumping device, and more particularly to a liquid toner concentrate dispenser.

2. Description of the Prior Art The toner solution in an eleetrophotographic development system consists of pigment particles suspended in a volatile solvent. The particles have a tendency to settle toward the bottom of the toner tank and to form gummy deposits on the exposed surfaces of the toner system. Preferably, the liquid toner is agitated to maintain toner circulation and prevent particle settling. Toner concentrate, the subject matter of the present invention, has a greater concentration of pigment particles and the effects of toner settling are more pronounced. The debilitating effect of the pigment sediment is particularly noticeable in check valves and moving parts with close tolerances.

The demand characteristics for toner concentrate in an electrophotographic toning system provides an addi tional restriction on toner concentrate dispenser designs. Toner concentrate is added to the toner tank periodically as toner depletion occurs due to developing or toning the electrophotographic charge images. The toner concentrate is normally added at intervals and is not provided on a continuous basis. Therefore, the pumping mechanism must be self priming and normally in a primed condition. The pump should be effective from the first cycle of operation when triggered by the toner demand schedule.

SUMMARY OF THE INVENTION It is therefore an object of this invention to provide a toner concentrate dispenser for an electrophotographic toning system which does not employ check valves or moving members with close tolerances; to provide above dispenser system which is self priming or normally in the primed condition; to provide the above dispenser the pumping mechanism of which is mounted on a cap member adapted to sealingly cooperate with the shipping bottle for the toner concentrate; to provide the above dispenser which agitates the sediment in the bottom of the toner concentrate flask during the dispensing action; to provide the above dispenser which is not subject to the debilitating effects of gumming and particle settlement.

BRIEF DESCRIPTION OF THE DRAWING Further objects and advantages of the present invention and the operation of the valveless toner concentrate dispenserwill become apparent from the following detailed description taken in connection with the drawings in which:

FIG. 1 is a schematic view of the toner concentrate dispenser mounted in the toning system of an electrophotographic duplicator; and

FIG. 2 is a sectional view of the valveless dispensing structure mounted inside the toner concentrate flask of FIG. I.

Referring to FIG. 1, there is shown an electrophoto graphic development system 10 including a pair of drive rollers 12 which cooperate with a rotatable toning drum 14 to pull a web 16 into temporary engagement with the surface of toning drum 14. Web 16 is formed by a paper base with a charge retentive layer thereover. The charge retentive has a charge image formed thereon by an electrophotographic imaging apparatus not shown. Toning drum 14 applies toner to this charge image by continuously rotating and dipping into the liquid toner 18 contained in toner tank 20. Toning drum 14 is a preferable wire mesh device and for absorbing liquid toner and elevating it to the region of web-drum engagement. The pigment concentration in toner tank 20 is sensed by a conventional pigment sensor 22 immersed in liquid toner l8. Toner concentrate demand signals generated by sensor 22 are applied to a reciprocating solenoid 24 mounted adjacent to developing system on bracket 26. The pulses activate solenoid 24 downward causing a walking beam 28 to pivot about a fulcrum 30 and move a hollow activating rod 32 upwardly. Activating rod 32 extends into flask 34 and is in liquid communication with the concentrate contained therein. The upward motion of hollow rod 32 initiates the first stroke of the toner pump contained within flask 34 during which toner concentrate is displaced from within flask 34 upwards through hollow rod 32. Activating rod 32, which also functions as a discharge tube, terminates in a downward direction hook portion 36 which extends into toner tank input lip 38. In summary, the toner demand signal from sensor 22 operates the dispenser causing concentrate to be distributed into toner tank 20 via concentrate input lip 38. Referring to FIG. 2, the detailed structure of the toner concentrate dispenser is shown in section. An elongated cylindrical housing 50 is secured at one end to cap member 52 and extends downward into flask 34. Cap member 52 cooperates with flask 34 in a sealing engagement facilitated by ring gasket 56 mounted in cap 52. A reciprocating piston 58 having piston head 58a and piston sidewalls 58b is mounted at the lower end of cylindrical housing 50 immersed in the toner concentrate 60 contained in flask 34. Piston 58 is secured to hollow activating rod 32 and reeiprocates up and down as rod 32 responds to solenoid 24. Piston 58 is normally in the lower or primed position as shown in the drawing. Chamber 62, formed by piston 58, housing 50 and a displacer core 64, is normally filled with toner concentrate which flows through chamber fill apertures 66 in the lower portion of side wall 58b. During the first stroke of dispenser operation, the displacement stroke, activating rod 32 is raised upward through the solenoid action described in reference to FIG. 1. Piston 58 subsequently is also raised and engages displacer core 64 secured to the inside of cylindrical housing 50. The toner concentrate in chamber 62 is forced into the hollow interior of activating rod 32 through chamber discharge ports 68 provided in activating rod 32. As piston 58 raises, fill aperture 66 moves past the lower end of housing 50 and becomes partially blocked attenuating the flow of toner concentrate which tends to discharge through fill aperture 66. During the second stroke of the dispenser action, the return stroke, activating rod 32 and piston 38 are lowered to their original positions by a return spring 67, and chamber 62 regains its original volume. Toner concentrate in activating rod 32 flows into chamber 62 and reestablishes the normally primed condition. A return stop collar 69 mounted on activating rod 32 abuts displacer 64 and determines the lower position of piston 58. Stop collar 69 prevents piston head 58a from dashing against the bottom of flask 34 and permits adjustment of the volume of the displacement stroke.

During the displacement stroke, piston sidewalls 58b move upward into a cavity 70 provided between cylindrical housing 50 and displacer core 64. Escape vents 72 are provided through cylindrical housing 50 to cavity 70 to allow toner concentrate to escape from cavity 70 while piston walls 58b are entering the cavity. Similarly, during the return stroke, piston sidewalls, 58b evacuate cavity 70 and vents 72 permit toner to reenter the cavity.

The controlled clearance between the working surfaces of piston sidewall 58b, displacer core 64 and the lower terminal portion of cylindrical housing 50 provides a controlled leakage jet of toner concentrate during the displacement stroke of the dispensing action. The toner concentrate leaks past the upwardly moving piston sidewall 58 and downard through the clearance between housing 50 and piston sidewall 58b towards the bottom of flask 34 where toner particles tend to settle. This periodic blast of leakage toner plus the up and down motion of piston 58 agitates the toner in the lower regions of flask 54. The continuous flow of toner through these controlled clearances, and in and out of cavity 70 prevent toner particles from settling on these working surfaces and prevents clogging or gumming. In addition, the controlled clearances eliminate surface to surface contact and the subsequent wear by attrition. The controlled clearance parts are cheaper to manufacture and easier to assemble.

Discharge tube or activating rod 32 extends through displacer core 64 and the afore described controlled clearance, sediment preventing flow is maintained between the working surfaces thereof. Concentrate which is discharged from chamber 62 upwards through this controlled clearance is returned to flask 34 through a leakage return vent 74. Vent 74 also provides access to set screw 73 mounted on return collar 69 for adjusting the position of collar 69 on activating rod 32.

It is preferred that variable capacity chamber 62 in a small dispenser have a maximum volume about one cc with a discharge output of about 0.75 cc per displacement stroke. The remainder of the chamber volume is consumed as leakage through the controlled clearances between the moving parts and the volume of discharge tube 32. The toner concentrate in discharge tube 32 at the end of the displacement stroke is not pumped out into development system but falls back into chamber 62. Preferably, this volume is minimized to eliminate as much as possible this inefficiency. Most of the leakage goes into forming the doward jet which agitates the toner concentrate sediment at the bottom of flask 34. The preferred tolerance between moving parts is about 2 mils for a small dispenser employing toner concentrate of usual viscosity. Larger dispensers and higher viscosity toner concentrate may require a 5 mil clearance or more.

Clearly, various changes may be made in the structure and embodiments shown herein without departing from the concept of the present invention. For example solenoid 24 could be mounted on cap 52 and activate rod 32 directly thus eliminating walking beam 28 and fulcrum 30. In addition, activating rod 32 could be activated regularly by a cam action eliminating the need for solenoid 24 and toner sensor 22.

it will be apparent to those skilled in the art that the object of this invention has been achieved by providing a toner concentrate dispenser having a reciprocating piston as the only moving part. Check valves are not employed. Controlled clearances are provided between moving surfaces to maintain toner flow and prevent gumming by particle settling. Toner concentrate flow through the controlled clearance agitates sediment on the bottom of the concentrate flask to eliminate sediment formation.

I claim as my Invention:

l. A device for dispensing toner concentrate to the developing system of an electrophotographic duplicator, comprising in combination:

a reservoir adapted to contain toner concentrate;

a variable capacity chamber immersed in the toner concentrate and positioned proximate the bottom of the reservoir and formed by an open-ended stationary shell member and a moveable piston member mounted proximate the open end thereof, the shell and piston members having a controlled clearance therebetween and cooperate in a two stroke dispensing action for supplying toner concentrate to the developing system and for providing controlled leakage of toner concentrate from the variable capacity chamber through the controlled clearance and out the open end of the shell for agitating the toner concentrate proximate the bottom of the reservoir, the movement of the piston member proximate the open end of the shell member providing further agitation of the toner concentrate proximate the bottom of the reservoir;

chamber flll aperture means provided in the stationary shell member for establishing fluid communication between the inside of the chamber and the toner concentrate in the reservoir for permitting toner concentrate to flow from the reservoir into the variable capacity chamber;

toner concentrate discharge means having one end .extending into the reservoir in fluid communication with the interior of the variable capacity chamber, the other end of the discharge means extending to the outside of the reservoir and adapted to supply toner concentrate to the developing system; and

chamber activating means connected to the moveable piston member for decreasing the volume of the chamber during the first stroke of the chamber forcing toner concentrate within the chamber into the discharge means and out of the reservoir to the development system, the chamber activating means increases the volume of the chamber during the second stroke forcing more toner concentrate from the reservoir to flow through the aperture fill means into the chamber.

2. The device of claim 1, wherein the moveable piston is mounted proximate the bottom of the reservoir and is activated in an up and down motion by the chamber activating means which agitates the toner concentrate proximate the bottom of the reservoir, and further wherein the controlled leakage is directed downward towards the toner concentrate at the bottom of the reservoir.

3. The device of claim 1, wherein the moveable piston has sidewalls defining the chamber and a stationary displacer member is positioned within the shell for penetrating the interior of the piston during the first stroke to displace toner concentrate from the interior of the piston into the toner concentrate discharge means, a receiving cavity is provided between the shell and the displacer to receive the piston sidewalls during the first stroke.

4. The device of claim 3, wherein the chamber fill aperture means is at least one aperture provided through the sidewalls of the piston, the fill aperture normally establishes fluid communication between the reservoir and the inside of the variable capacity chamber, the fill aperture is blocked by the shell as the piston moves therein to cause the fluid communication between the reservoir and the interior of the chamber to attenuate.

5. The device of claim 4, wherein vent means are provided in the shell to establish fluid communication between the receiving cavity and the reservoir for permitting displacement of toner concentrate from the cavity into the reservoir as the piston sidewalls enter the cavity during the first stroke and to further permit toner concentrate to return into the cavity from the reservoir as the piston sidewalls evacuate the chamber during the second stroke.

6. The device of claim 5, wherein the activator means is a connecting rod extending from the piston through the displacer and outside of the reservoir where the connecting rod is adapted to be moved reciprocally to activate the chamber.

7. The toner concentrate dispenser of claim 6, wherein the activator rod is hollow and functions as the toner concentrate discharge means in addition to functioning as a connecting rod. 

1. A device for dispensing toner concentrate to the developing system of an electrophotographic duplicator, comprising in combination: a reservoir adapted to contain toner concentrate; a variable capacity chamber immersed in the toner concentrate and positioned proximate the bottom of the reservoir and formed by an open-ended stationary shell member and a moveable piston member mounted proximate the open end thereof, the shell and piston members having a controlled clearance therebetween and cooperate in a two stroke dispensing action for supplying toner concentrate to the developing system and for providing controlled leakage of toner concentrate from the variable capacity chamber through the controlled clearance and out the open end of the shell for agitating the toner concentrate proximate the bottom of the reservoir, the movement of the piston member proximate the open end of the shell member providing further agitation of the toner concentrate proximate the bottom of the reservoir; chamber fill aperture means provided in the stationary shell member for establishing fluid communication between the inside of the chamber and the toner concentrate in the reservoir for permitting toner concentrate to flow from the reservoir into the variable capacity chamber; toner concentrate discharge means having one end extending into the reservoir in fluid communication with the interior of the variable capacity chamber, the other end of the discharge means extending to the outside of the reservoir and adapted to supply toner concentrate to the developing system; and chamber activating means connected to the moveable piston member for decreasing the volume of the chamber during the first stroke of the chamber forcing toner concentrate within the chamber into the discharge means and out of the reservoir to the development system, the chamber activating means increases the volume of the chamber during the second stroke forcing more toner concentrate from the reservoir to flow through the aperture fill means into the chamber.
 2. The device of claim 1, wherein the moveable piston is mounted proximate the bottom of the reservoir and is activated in an up and down motion by the chamber activating means which agitates the toner concentrate proximate the bottom of the reservoir, and further wherein the controlled leakage is directed downward towards the toner concentrate at the bottom of the reservoir.
 3. The device of claim 1, wherein the moveable piston has sidewalls defining the chamber and a stationary displacer member is positioned within the shell for penetrating the interior of the piston during the first stroke to displace toner concentrate from the interior of the piston into the toner concentrate discharge means, a receiving cavity is provided between the shell and the displacer to receive the piston sidewalls during the first stroke.
 4. The device of claim 3, wherein the chamber fill aperture means is at least one aperture provided through the sidewalls of the piston, the fill aperture normally establishes fluid communication between the reservoir and the inside of the variable capacity chamber, the fill aperture is blocked by the shell as the piston moves therein to cause the fluid communication between the reservoir and the interior of the chamber to attenuate.
 5. The device of claim 4, wherein vent means are provided in the shell to establish fluid communication between the receiving cavity and the reservoir for permitting displacement of toner concentrate from the cavity into the reservoir as the piston sidewalls enter the cavity during the first stroke and to further permit toner concentrate to return into the cavity from the reservoir as the piston sidewalls evacuate the chambEr during the second stroke.
 6. The device of claim 5, wherein the activator means is a connecting rod extending from the piston through the displacer and outside of the reservoir where the connecting rod is adapted to be moved reciprocally to activate the chamber.
 7. The toner concentrate dispenser of claim 6, wherein the activator rod is hollow and functions as the toner concentrate discharge means in addition to functioning as a connecting rod. 